Study on the exergy efficiency and hydrogen production rate in biomass gasification process based on pilot-scale

Global energy challenges, driven by rising demand and environmental concerns, underscore the need for sustainable alternatives like hydrogen energy. Biomass gasification, particularly through thermochemical processes, offers a promising pathway for hydrogen production. Previous studies, no researchers have comprehensively analyzed the interrelationship between exergy efficiency (ExE) and hydrogen production rate (HPR). This study addresses these gaps by analyzing the effects of key parameters, including gasification temperature, equivalence ratio (ER), steam-to-carbon ratio (SCR), and gasifying agent, on HPR and ExE using experimental data from multiple pilot-scale gasification devices, such as fixed bed and fluidized bed systems. The results indicate that an optimal gasification temperature range (800-1000 °C), an optimal ER range (0.21-0.38) and an optimal SCR range (1.3-2.46) can simultaneously enhance HPR and ExE. Steam as a gasifying agent significantly increases HPR. However, pure steam gasification reduces ExE due to its endothermic nature, while combining steam with oxygen achieves a balance between high HPR and improved ExE. Due to superior heat transfer and fluidization effects, fluidized beds maintain relatively high ExE even at lower temperatures, whereas fixed beds, owing to longer reaction times and more complete gasification, can achieve higher temperatures and higher HPR. The relationship between HPR and ExE varies depending on the type of gasifier: it follows a parabolic pattern in fluidized beds, while tending to be more linear in fixed beds. The outcomes of this study offer insights for advancing the development of efficient and sustainable biomass gasification systems, thereby facilitating the global transition to clean energy.